The present disclosure is generally related to a hexafluorodimethylcarbinol terminated thiol compound, to a precursor for forming the compound, to a general synthetic procedure for forming the compound, and to a sensor device which incorporates the compound.
Fluoroalcohol and thiol functional groups confer unique properties on molecular substances, which qualify them for many applications. The unique properties associated with incorporation of the fluoroalcohol functional group include strong hydrogen bonding interaction and proton acidity coupled with a hydrophobic character. This combination of properties makes fluoroalcohol substituted compounds surface active agents in aqueous systems and, as such, they find applications as surfactants, wetting and dispersing agents, defoamers, phase transfer agents, and polymer blend formation promoters, etc. For detection of the organophosphorus chemical warfare agents, the hydrogen bonded interaction of the fluoroalcohol alcohol with the phosphoryl group is advantageous for the sensitivity and selectivity of point sensors in this application. The thiol functional group is beneficial for its coordination with metal ions and for its coordination with neutral metals. As such, the covalently bonded adsorption of thiol functionalized molecules to metal surfaces has been extensively used as a metal surface treatment, and it has found many applications that include nano- and molecular electronics, soft lithography, contact printing, nano-particulate composites, chemical sensing, corrosion resistance, adhesion promotion, and electrochemistry. Numerous ω-functionalized n-alkenethiol compounds have been synthesized and investigated for properties and applications involving metal surfaces.
One particular application is in chemical species detection, which has led to developments of sensor assemblies that include a film of core-ligand material. U.S. Pat. Nos. 6,221,673 and 7,347,974, to Snow, et al., disclose one such chemical sensor assembly, wherein metal or metal alloy nanoparticles are encapsulated by a monomolecular layer of ligand molecules. The ligand molecule has a chain structure with a thiol functional group at one end and a heteroatom functional group at the other end. The thiol group bonds to a metal atom of the nanoparticle surface, and this heteroatom functional group interacts with vapors in the environment. In these disclosures, the heteroatom functional group is a hexafluorodimethylcarbinol structure.
A trifluoromethylcarbinol terminated thiol is disclosed in U.S. Pat. No. 7,189,867 ('867), to Wynne, et al. This compound was designed from the same considerations dating back to use of the hexafluorodimethylcarbinol in polymer coatings for sensor applications described in Snow et al, J. Appl. Poly Sci. 43, 1659 (1991). The '867 patent discloses a molecular agent for monomolecular coatings on metal and metal oxide surfaces. The compound is of general formula CF3—CH(OH)—CH2-(L)n-CH2—SH, wherein L can be a substituted or unsubstituted methylene, a substituted or unsubstituted oxyalkylene, or an alkyl-substituted or unsubstituted siloxanylene. The '867 disclosure includes a synthetic procedure for forming the compound.